Patients with a poor response to initial therapy with prednisone receive maintenance therapy comprising oral mercaptopurine daily for weeks 1-14; oral methotrexate once weekly for weeks 1-14; oral dexamethasone three times daily for weeks 1 and 2; vincristine IV on day 2 of weeks 1 and 2; etoposide IV over 2 hours once weekly on weeks 8 and 9; and cytarabine IV over 1 hour once weekly on weeks 8 and 9.